Safety pressure relief device



March M. E. BONYUN ET AL 1 4,159

SAFETY PRESSURE RELIEF DEVICE Filed Nov. 30, 1958 I iLIJIIIII lidINVENTORS Mclr'gan E.E|un1 q un James F. Andrews ATTORNEY Patented Mar.19, 1940 UNITED STATES SAFETY PRESSURE RELIEF DEVICE Morgan Evan Bonyun,

Penns Grove, N. J., and

James F. Andrews, Chester, Pa., assignors to E. I. du Pont de Nemours &Company, Wilmington, Del., a corporation of Delaware ApplicationNovember 30, 1938, Serial No. 243,266

4 Claims.

This invention relates to a pressure relief device for a container inwhich pressure may be produced suflicient to burst the container. Moreparticularly the invention relates to that type 5 of safety device forpressure relief commonly known as a frangible disc. It is an object ofthe invention to provide an improved device of this nature which willfunction more accurately under varied conditions than pressure reliefmeans of a comparable sort previously used and known. Other objects willbe pointed out in the description of the invention or will be apparenttherefrom. A full understanding of our invention by which these objectsare accomplished may be had from the accompanying drawing, and thedescription which follows:

Referring to the drawing which forms a part of this specification, Fig.I shows a vertical central sectional view involving a preferredembodiment of our invention and Fig. 11 shows a similar view except thatthe relief device and supporting members are in assembled position readyfor use. Figure 111 is a central cross sectional view of the pressurerelief device alone.

For conveniently describing the safety device it will be referred to asa hydraulic capsule. In the different figures of the drawing like partsare designated by like numerals. The opposed concave-convex discs whichform the walls of the hydraulic capsule of applicantsv invention aredesignated respectively by numerals l and 5. A circular groove in themarginal area of the frangible discs is indicated by 6. The number 7refers to the liquid filling agent of the hydraulic capsule. Numbers 8and 9 designate, respectively, the two parts of a suitable ring-formholder or support for the hydraulic capsule of Fig. III. Numberrepresents retaining screws for holding together the two parts of thehydraulic capsule support. A male annular seating projection on thesealing face of ring 8 is numbered II, and I2 designates an annularfemale sealing groove in ring 9.

Flanges l3 and I4 and flange-retaining bolts l5 illustratea suitablemeans for retaining the hydraulic capsule in a pressure line.

Having identified the various details in the.

drawing, we will proceed with the description of the invention.

Frangible discs I and 5 provide pressure relief by rupturing whenexcessive pressure develops. They are readily replaceable and may bemade of any material having sufflciently uniform and otherwise suitablephysical properties. Ordinarily metals will be used, such as nickel,copper,

aluminum, silver, platinum, gold and lead. The nature of the corrosiveaction, if any, of vapors to which the hydraulic capsule is exposed,pres-' sures to be retained, temperature of operation and size of ventare all factors on which the choice of a suitable material for thefrangible discs depends.

The frangible discs 4 and 5 are cut from sheet stock which may be flator may have been previousiy bulged. In the event that the discs are madefrom fiat stock, they must be placed between the hydraulic capsuleholders 8 and 9 one by one and bulged to a perfect spherical segment.Pressure is applied from the under side to bulge disc 4 and from theupper side to bulge disc 5. The magnitude of pressure used iscomparatively unimportant provided it is in excess of that formed byvacuum and sufiiciently below the bursting pressure of the disc to allowadditional expansion due to temperature change. For example, a discdesigned to burst at 50 pounds per square inch has proved satisfactorywhen hydraulically bulged at 35 pounds per square inch.

To fill and assemble applicants hydraulic capsule for use, one mayproceed as follows: the hydraulic capsule holder composed of rings 8 and9 and retaining screws it, is submerged in a container filled with thehydraulic medium 6 to a depth to provide a slight pressure such as 1 lb.per square inch. The holder is then manipulated and rubbed to free it ofbubbles and the frangible discs 4 and 5 are submerged, freed fromadhering bubbles, if any, and placed in their respective positions inthe holder, with concave faces toward each other. The retaining screwsill of the holder are then tightened to seal the liquid inside thecapsule. The sealing is facilitated by the sealing ridge H of holder 8which forces metal of the frangible discs into the receiving circulargroove l2 of holder 9.

Liquid filling medium for the hydraulic capsule may be any substantiallynon-compressible fluid suited to the particular operation in which thedevice is to be used: for example, water, glycerine, mineral oil andanimal and vegetable oils.

It is to be understood that various methods of forming and filling thehydraulic capsule 1. 1y be resorted to and such are no part of theinvention. Applicants desire protection only for the frangible dischydraulic capsule and its use regardless of the methods employed to formand fill it.

After the hydraulic capsule is filled and assembledwith the holder, thewhole may be fastened between pipe flanges I3 and M by tight-- eningbolts l5. Flanges l3 and H are shownin the drawing as having a pipe tapto accommodate threaded pipes leading from a pressure vessel to thesafety device and thence to a discharge area or receiving tank orheader.Naturally various modifications are optional for particular service. Forexample, one flange may be integrally formed with the pressure vessel,and where the discharge is not obnoxious and without value, a dischargepipemay be dispensed with.

Although the hydraulic capsule is conveniently formed, filled, andmounted in a holder, as explained above, it may be independently filledand inserted between flanges in a pressure line. When a holder is notused, the capsule may be filled by submerging it and sealing it underthe liquid with a suitable tool. For example, one disc may be madeslightly greater in diameter and an upturned rim on the larger disc maybe folded over and crimped on the rim of the other disc. Appropriategrooves made in the pipe flanges will accommodate the bead on the rim ofthe hydrauic capsule when this procedure is employed. When the fillingliquid is sufllciently viscous and the hydraulic capsule is to beinserted without delay between flanges in a pressure line, the naturaladherence of the wet disc flanges is all that is necessary to preventingress of air.

In the drawing and thus far in the description applicants hydrauliccapsule has been represented as having the component frangible discsmounted rim to rim. It should be understood, however, that by suitablemodification of the holder or otherwise the pair of discs may be mountedwith some inter ening space between their rims and still functionsatisfactorily. This is ahighly distinguishing feature betweenapplicants hydraulic capsule containing a substantially non-compressiblefluid and a pair of similar frangible discs enclosing air or any easilycompressible gas.

The hydraulic capsule, as described herein, is particularly applicablewhere a safety bursting between and 200 pounds pressure is required. Itis known that the action of a given pressure on a convex surface exertsconsiderably greater sin-es than on a concave surface. For this reasonfrangible discs of the type under consideration designed to burst withinthe above mentioned range collapse prematurely lmder vacuum or backpressure fromacommon discharge header. The hydraulic capsule of'thepresent invention obviates this trouble-sincethe stress, due to reversalof pressure, is transmited through the practically incompressible liquidto,the stronger concave section. In other words, the bursting point ofapplicants hydraulic capsule is the same regardless of the directionfrom which the pressure is applied, thus effectively protecting againstpremature rupture on reversal of pressure. For example, if a 2" diameter.003" thick aluminum disc is employed, it is calculated to rupture at 43pounds positive pressure. In the form of applicants hydraulic capsulethis occurs no matter from which side the pressure comes. Vacuum cannotexceed 14.! pounds per square inch so it can have no effect on thehydraulic capsule, but if a single disc is substituted, it will stillrequire 43 pounds pofltive to rupture it, but only 7% pounds(approximately. 15" of mercury) reversed or negative pressure. The 7%lbs. of negative pressure is not the rupture pressure, but is the pointat which the disc will reverse its contour and-break the metal at theedge of the disc..

Having thus described our invention and application of the same, what weclaim as new and desire to protect by Letters Patent of the UnitedStates, is:

1. 'An excess pressure releasing device comprising a. supporting memberhaving a discharge passage for excessive pressure therethrough and apair of concave-convex frangible discs mounted to normally close thepasage, said frangible discs being arranged with their concave facestoward each other and having the sealed intervening space between thediscsfilled with a substantially incompressible fluid.

2. An excess pressure releasing device comprising a supporting memberhaving a discharge passage for excessive pressure therethrough, aring-shaped holder in which is mounted a pair of concavo-convexfrangible discs with concave faces toward each other and having thesealed intervening space between the discs filled with a substantiallyincompressible fluid, said supporting member and annular holdermaintaining the frangible discs and their liquid content in a positionto normally close the discharge passage. 3. An excess pressure releasingdevice comprisingasupportingmemherhavingadischarge passage for excesspressure therethrough and a pair of concavo-convex metal frangible discsfixed to normally close the e, said metal frangible discs being arrangedwith their concave faces toward each other and having the sealedintervening space between the discs filled with a substantiallyincompressible fluid.

4. An excess pressure releasing device consisting of a presure dischargeoutlet normally closed by a pair of concavo-convex frangible discsarranged with their concave faces toward each other and having thesealed intervening space between the discs filled with a substantiallyincompressible fluid.

. MORGAN EVAN BONYUN.

JAMES F. ANDREWS.

